A growing body of human epidemiologic evidence links intrauterine growth retardation (IUGR) and adult "Syndrome X": hypertension, obesity, diabetes, coronary artherosclerosis, and risk of renal failure. In preliminary studies in microswine, maternal isocaloric protein restriction (0.5% vs. 14%) during nephrogenesis (last 1/3 gestation +3 weeks post- natally) yields IUGR at 3 weeks, rapid catch-up growth to 123% of control body weight (overweight), adult hypertension, reduced nephron number by histology, and normal GFR suggesting single-nephron hyperfiltration. Renal cortical AT1 and AT2 receptors by quantitative autoradiography are abnormal in both 3-week and 6-month old offspring of low-protein sows but in unique ways. We hypothesize that excess appetite/body image size generate excess protein load for the low number of nephrons, driving sustained intrarenal renin/AngII (RAS) activation to achieve nitrogen balance via single-nephron hyperfiltration. This RAS response is predicted to amplify the Na retention and extracellular fluid volume (ECV) excess expected with fewer nephrons, yielding hypertension. In a microswine model of maternal protein restriction/IUGR, studies in offspring will address: 1) whether IUGR modifies the activation state of circulating vs. intrarenal RAS at key developmental stages (preterm; 2-weeks postnatal; 3-month pre- hypertensive juvenile; and 6-month adult), including mRNA, protein, and activity levels for renin, angiotensinogen, ACE, AngII, and AT1/AT2 receptors at Low-Protein vs. Normal-protein offspring on ad lib normal diet; 2) whether IUGR enhances postnatal homeostatic responses of blood pressure (BP), ECV, Na balance, and circulating vs. intrarenal RAS components in vivo to dietary sodium manipulation to AngII blockade; 3) whether IUGR amplifies AT1 signaling efficacy in vitro in cultured vascular smooth muscle at each developmental stage; and 4) whether global caloric restriction to limit adult bodyweight to 75% of Normal-protein controls in IUGR offspring attenuates adult BP, body fat mass, ECV, and intrarenal RAS components. Results are relevant to etiologic mechanisms of hypertension and to the preventive management of IUGR-exposed children at risk for adult cardiovascular and renal disease.